Apparatus for the production of powders of low-melting-point metals or of compounds thereof



. 2,213,365 -MELTINGPOIN'I S. HILLER APPARATUS FOR THE PRODUCTION OF POWDERS OF LOW METALS 0R OF COMPOUNDS THEREOF Filed Jan. 24, 1939 I I I 35 product falls into a precipitating chamber.

Patented Sept. 3, 1940 UNITED STATES APPARATUS FOR THE PRODUCTION OF POWDERS OF LOW-MELTING-POINT DIETALS B. OF COMPOUNDS THEREOF Siegfried Hiller, London, England Application January 24, 1939, Serial No. 252,678 In Great Britain September 30, 1938 Claims.

' This invention relates to apparatus for the production of fine powders of low-melting-point metals or compounds thereof, in particular of metallic lead or lead oxides.

There is known apparatus for making lead oxide in which the lead is melted in an externally heated vessel, is atomised by being whirled against the walls of the vessel by the blades of a stirring device acting upon the surface of the lead vertically or obliquely, or by percussion devices dippinginto the surface of the molten lead, and the lead is oxidised by the introduction of hot air or superhe ted steam or a mixture of air and steam. According'to another proposal a centrifugal wheel dipping into a lead bath is formed as a fan for drawing in the current of gas necessary for conducting away the resulting leadoxide dust, and blades secured to the centrifugal wheel fit, as closely as possible, part of the internal surface of a pear-shaped oxidation chamber inclined upwardly from the lead bath for the purposeof scraping loose lead oxide adhering to the internal surface of the oxidationchamber. In each of these known apparatus the metalmelting vessel and the atomising or oxidation chamber are built-in in such a manner that the atomising devices are very diflicult of access and therefore much-trouble is involved in repairing any injury to the parts in question. There is 30 also known an apparatus for the making of lead oxide in which the lead flows from the melting vessel into a centrifugal mill, which is formed as a fan and in which the atomised lead is oxidised by means of drawn-in air, whilst the resulting This apparatus is attended by the disadvantage that incrustation is apt to occur in the conduit through which the liquid lead passes into the centrifugal mill in the centrifugal mill itself. A further dis- 45 sion of apparatus for the purpose above indicated.

from which the centrifugal device can be easily removed for purposes such as repair or cleaning, from the melting vessel. A further object is the 50 construction of the centrifugal device as a unit. A further object is improving the facilities for attending to and charging the melting vessel. Yet another object is the provision for the purpose indicated of a centrifugal device which re- 55 ceives the molten metal merely by partial immersion; and in which provision exists for the return and further comminution of such metal as may be above certain grades of size after treatment, this being accomplished by simple gravitational means.

vIn apparatus according to the invention the centrifugal device can be easily removed and repaired or cleaned away from the furnace and the metal-melting vessel, whilst the melting furnace and the melting vessel can be used if required for 10 other purposes after the removal of the centrifugal device. Further, the melting furnace and the melting vessel can be easily attended to and changed.

Now an apparatus for the purpose in'question 16 according to the invention, comprises an externally heated metal-melting vessel and a fllnger device which is arranged so that molten metal will flow into the atomising chamber or casing of the said device through an opening or openings 20 in the lower portion of the said chamber and be acted upon by the rotary portion of the said device; and which may be constructed as a unit and adapted to be readily removable independently'of the metal-melting vessel.

Moreover the outlet portion of the peripheral wall of the atomising chamber is preferably streamlined in the direction of outward and upward travel of the metal particles for a purpose hereinafter stated. For the purpose of the sift- 80 ing of the products by gravity the outlet of the centrifugal atomising chamber has connected to it a vertical upwardly extending chamber through which the light particles are carried in opposition to the action of gravity by a. current of gas, whilst coarse particles drop directly into the atomising chamber, where they are further comminuted so that only the finest particles are carried by the current of gas into a connecting chamber. The material is thus completely treated so 40 that there is no inferior product that must be removed. It is usually unnecessary to grind the resultantproduct even if it is to be used for the making of paint.

The invention is illustrated by the accompanying diagrammatic drawing. which representsan example of apparatus according thereto which is suitable both for the production of finely divided lead or lead dust, an also for the production of oxidation products of lead; Figure 1 is a sec- 60 tion corresponding to the line ll of Figure 2, ,and Figure 2 Ba section corresponding to the line ll-ll of Figure 1.

In a furnace I there is inserted a vessel 2 in which the lead is melted. The centrifugal atomising device comprises a rotary wheel '3, having radial vanes 3a, and an atomising chamber or casing 4 having a peripheral wall 4a carried by the shaft 3b of the wheel 3, which shaft is mounted in bearings 3c which are, for example, removably bolted to the ,wall of the furnace I, and is driven, for example by electric motor. The shaft lb has a coupling 3d for'readily coupling the source of power; or it may have a pulley for a belt, or other driving means. The wall 4a has, at the botto'm thereof, openings 5 which may, as shown, be provided with short outwardly projecting tubes in, for the entry of molten metal from the vessel 2 into the atomising chamber so that at least the vanes of the rotary portion 3 dip into and act directly upon the molten metal which has fiowed thereinto. The

outlet portion of the-peripheral wall 4a of the casing is stream-lined in the direction of outward and upward travel of the metal particles, in accordance with the direction of rotation indicated by the arrow on the wheel 3, so as to facilitate the upward travel of the particles and also the.

falling back of the larger particles into the centrifugal device for further comminution; the remainder of the wall 4a is concentric with the wheel 3. The end walls of the casing 4 are advantageously bolted to the peripheral wall 4a so as to render the interior of the centrifugal device easily accessible for repair or cleaning. 1

atomising device of heavy particles that have been thrown upwards by the wheel 3 of the centrifugal device'is assisted and the sifting is improved.- In this chamber there may be provided bailies for assisting the sifting of the material. The chamber 6 ends in a delivery tube 1 which leads to an ordinary collecting vessel (not shown) If the powdered metal is to be oxidised, there is introduced through a pipe 8 into a conduit 8a, 9b, heated air orsteam or a mixture of air and steam or some suitable oxidising gas, for the suction of which there may serve the wheel 3 of the centrifugal device if it is, as shown, formed as a fan. The conduit 9a, 9b, is composed of two parts 90. and 9b which are connected together by a flange joint 90 so asto be'easily disconnectible'to enable the whole centrifugal device to be removed as a unit when necessary. The part 9?) serves as the mounting for securing the chamber 4 in the desired position, and preferably joins the casing 4 axially, as seen in Figure 2..

The wheel 3 has any required known formation.

For the purpose dff'tillsingthb' heat' of the waste gases of the furnace that-heats the metal in the vessel 2, those gases may be'i'ntroduced through an outlet l0 and a conduit ll "into the conduit 8a, 9b,. so that the heat of those gases to act as a centrifugal blower, and to suck gases i will serve for maintaining the desired temperatur'e (which is usually somewhat above the meltduced into the atomising chamber, be freed from dust by means of a filter I! or be otherwise purified. A valve l4 enables the supply of the waste gases to be regulated or stopped; when stopped by the valve l4 they may be allowed to escape past a valve l2, into a flue. The supply of airor steam is regulated by a valve I 3.

The operation of the apparatus is as follows in thecase of the production of lead oxide:

By the wheel 3 of the atomising device molten lead, of which the surface is shown at 241, well above the lowest point to which the vanes 3a extend, is thrown against the wall 4a of the atomising chamber and the resulting particles of comminuted metal are projected into the chamber 6. The metal particles e at the same time oxidised by drawn-in ho gases or steam and the oxidation products are transported by the current of gas or steam through the chamber 6 and led away through the pipe I, whilst the unoxidised'relatively heavy metal particles drop back directly into the atomising chamber and are further comminuted therein. In this way there is obtained lead oxide in a state of very fine division, which can be used as it is for decorative or anti-rust paints or converted into red. lead without further grinding or used for other purposes, for example for making masses for accumulators.

The apparatus according to the invention may be used also for the making of other finely divided lead compounds for example lead carbonate, for which carbonic acid and air are introduced into the atomising chamber.

In the case of the manufacture of finely divided metallic lead the operation is the same except that the supply of oxidising gas or steam is omitted and the carrying away of the metal powder is effected by means of non-oxidising .gases, for example carbon monoxide or nitrogen,

or reducing gases, as the reducing waste gases from the melting furnace.

Apparatus according to the invention may be similarly used for the obtaining in a finely divided form or other low-melting-point metals, as tin, antimony, or cadmium, and their compounds.

What I claim is:

1. In apparatus for finely comminuting molten metal in a melting vessel, a comminuting unit partially immersible in said vessel comprising a rotatable flinger wheel and a casing therefor with an inlet in the bottom thereof through which molten metal from the said vessel can enter the casing, and anoutlet passage at the upper part of the casing through which finely comminuted metal is projected, the bottom part of the casing extending underneath said flinger .wheel in conformity with and in close proximity to the periphery thereof.

2. Apparatus for finely comminuting molten -metal comprising in combination a rotatable fiinger wheel, a casing forming a comminuting unit therewith adapted to be partially immersi-' ble in a bath of molten metal in a melting vessel, an inlet in the bottom of said casing through which molten metal can flow from said vessel into said casing into contact with said fiinger wheel and an outlet at the upper end of the easing through which finely comminuted metal is projected, said casing extending underneath said {wheel in conformity with and in close proximity "to the periphery thereof.

3. In apparatus for the production of powders of low-meltingpoint metallic products including a metal melting vessel, a comminuting unit and partially immersed in molten metal therein,

comprising in combination a rotatable fling er wheel, a casing extending underneath said wheel in conformity with and in close proximity to the periphery thereof, an inlet "at the bottom of the casing, an outlet at the upper part of the casing, driving means for said fiinger wheel and means for supporting said wheel and casing in a readily detachable manner relative to the melting vessel and in a partially immersed condition so that metal can flow into the casing into contact with the fiinger wheel to be finely comminuted and projected thereby.

4. Apparatus for the production of powders of lowmelting-point metallic products, comprising in combination a casing having an inlet in the bottom thereof, a fiinger wheel rotatably mounted in a vertical plane in said casing, radial vanes on said wheel, a substantially vertical outlet duct associated with said casing, and means for mounting said wheel and casing in a readily detachable manner on a separate melting vessel a part ofthe casing extending underneath said wheel in close proximity toasaid vanes so that the metal flowing into the casing through said inlet is finely comminuted and projected throughthe outlet duct by the fiinger wheel. I

5. In apparatus for the production of pow ders of low-melting-point metallic products, a comminuting unit comprising in combination a 1'0- tatable flinger wheel, and a substantially cylindrical casing therefor with an inlet for molten metal at the bottomand an outlet duct at the top, the lower part of said casing conforming with and being in close proximity to the periphery of said wheel for an angular measure of at least 180, and being partially immersed in molten metal in a separate melting vessel so that metal flowing through said inlet is finely comminuted between the wheel and the casing.

' SIEGFRIED HILLER. 

